1. Field of the Invention
The present invention relates to a control system for charging on-board power storage devices for driving vehicles, to a control device, and to a cable connection state determining method.
2. Description of the Related Art
Attention has been given in recent years to environment-conscious vehicles such as electric vehicles, hybrid vehicles, and fuel cell vehicles. These vehicles are equipped with electric motors for generating power to drive the vehicles and power storage devices for storing power supplied to the electric motors. Hybrid vehicles are further equipped with internal combustion engines as power sources in addition to the electric motors, while fuel cell vehicles are equipped with fuel cells as vehicle-driving DC power sources.
Some of the foregoing vehicles are known to be able to charge the vehicle-driving power storage devices directly by domestic power sources. For example, power is supplied from the domestic power source to the power storage device through a charging cable connected between a receptacle of commercial power source in a residential house and a charging port of the vehicle. Those vehicles capable of charging the on-board power storage devices directly by external power sources are referred to as “plug-in vehicles.”
Japanese Unexamined Patent Publication No. 9-161882 proposes an electric-automobile charging connector that provides for improved resistance against drop impact of a feeder side connector repeatedly fitted to a receiving side connector.
Standards for the plug-in vehicles are established in the United States by “SAE Electric Vehicle Conductive Charge Coupler” (November 2001, SAE Standards, SAE International).
In Japan, the standards for the plug-in vehicles are established by “General Requirements for Electric Vehicle Conductive Charging System (Mar. 29, 2001, Japan Electric Vehicle Association Standard).”
“SAE Electric Vehicle Conductive Charge Coupler” and “General Requirements for Electric Vehicle Conductive Charging System” define standards regarding, for example, control pilot.
The control pilot is defined as a control line connecting a control circuit for EVSE (Electric Vehicle Supply Equipment), which supplies power from a premises wiring to the vehicle, and a ground portion of the vehicle through a vehicle-side control circuit.
A pilot signal transmitted through the control line is used a basis for, for example, detecting the state of connection of the charging cable, determining whether power can be supplied from the power source to the vehicle, and detecting the rated current of the EVSE.
However, “SAE Electric Vehicle Conductive Charge Coupler” and “General Requirements for Electric Vehicle Conductive Charging System” do not particularly define details of how to detect a break of the control line through which the pilot signal is transmitted.
For example, when the potential of the control line is at ground level, this cannot be differentiated between a break of the control line, failure of the power source outside the vehicle, unintentional disconnection of the charging cable off the receptacle, and other causes.
Thus, when the charging cable is connected but the power storage device is not charged, the user is not aware of this situation until the power storage device is in a discharged state. This forces the hybrid vehicles to run only on fuel such as gasoline to the detriment of mileage.
The pilot signal is a requisite signal for controlling charging of plug-in vehicles. It is therefore vital to detect abnormality in the pilot signal, especially a break of the control line through which the pilot signal is transmitted.
In order to secure that a control device at the vehicle side is able to detect whether the charging cable is connected to the vehicle, the charging cable is provided with a connection determination circuit that indicates an ON state as normal state. This connection determination circuit includes a switch connected in series with a resistive element and a resistor so that the control device at the vehicle side is able to detect whether the charging cable is connected to the vehicle on the basis of output from the connection determination circuit.
However, since the switch is configured to turn off in conjunction with an operation portion for connecting and disconnecting the charging cable to and off the vehicle, such a problem arose that differentiation cannot be made between a state in which the charging cable has been disconnected off the vehicle and a state in which the operation portion is being depressed while the charging cable is being connected to the vehicle.
Specifically, the operation portion is an operation button for making an open operation of a mechanical lock mechanism when disconnecting a connector of the charging cable locked to the charging inlet located at the vehicle side by the lock mechanism. When the operation button is depressed, the switch turns off in conjunction with the depression, and thus it is impossible to differentiate between the state in which the connector has been actually pulled out of the inlet and the state in which the operation button is being depressed.
In view of this, in the case where the control device at the vehicle side is able to determine that the charging cable is not connected to the vehicle on the basis of output from the connection determination circuit, the control device may determine whether the charging cable is disconnected of the vehicle on the basis of the signal level of the pilot signal.
However, a proper determination cannot be made in the case of a break of a signal line for the pilot signal or in the case a failure of the external power source. Additionally, a proper determination cannot be made in the case where the charging cable is not connected to the external power source. Thus, there is a need for making a detection of state of insertion or disconnection of the charging cable to or off the vehicle, regardless of the signal level of the pilot signal.